Fix iOS build

Author: timunie

src/Avalonia.Samples/CompleteApps/AdvancedToDoList/AdvancedToDoList.iOS/AppDelegate.cs

@@ -4,6 +4,7 @@
 using Avalonia.Controls;
 using Avalonia.iOS;
 using Avalonia.Media;
+using AdvancedToDoList.iOS.Services;
 
 namespace AdvancedToDoList.iOS;
 

src/Avalonia.Samples/CompleteApps/AdvancedToDoList/AdvancedToDoList.iOS/Services/IosDatabasePathService.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Threading.Tasks;
 using AdvancedToDoList.Services;
 
 namespace AdvancedToDoList.iOS.Services;